feat(protocol): grammatica S-expression (15 verbi) + parser

Aggiunge il modulo `multi_swarm.protocol` con la grammatica del DSL di
strategia (15 verbi: 4 azioni, 3 logici, 3 comparatori, 4 dati, `when`
e `strategy`) e un parser che produce un AST tipizzato (Strategy/Rule/
Node). Lessing delegato a sexpdata, validazione del set di verbi e
forma `(when <cond> <action>)` gestita dal parser. Sollevata ParseError
su top-level malformato, strategia vuota, verbi sconosciuti o azioni
non terminali.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/test_protocol_parser.py

@@ -0,0 +1,47 @@
+import pytest
+
+from multi_swarm.protocol.grammar import VERBS
+from multi_swarm.protocol.parser import ParseError, parse_strategy
+
+
+def test_grammar_has_15_verbs():
+    assert len(VERBS) == 15
+
+
+def test_parse_simple_strategy():
+    src = "(strategy (when (gt (indicator rsi 14) 70.0) (entry-short)))"
+    ast = parse_strategy(src)
+    assert ast.kind == "strategy"
+    assert len(ast.rules) == 1
+    rule = ast.rules[0]
+    assert rule.kind == "when"
+    assert rule.condition.kind == "gt"
+    assert rule.action.kind == "entry-short"
+
+
+def test_parse_multiple_rules():
+    src = """
+    (strategy
+      (when (gt (indicator rsi 14) 70.0) (entry-short))
+      (when (lt (indicator rsi 14) 30.0) (entry-long)))
+    """
+    ast = parse_strategy(src)
+    assert len(ast.rules) == 2
+
+
+def test_parse_unknown_verb_raises():
+    src = "(strategy (when (frobnicate 1 2) (entry-long)))"
+    with pytest.raises(ParseError):
+        parse_strategy(src)
+
+
+def test_parse_malformed_raises():
+    src = "(strategy (when"
+    with pytest.raises(ParseError):
+        parse_strategy(src)
+
+
+def test_parse_empty_strategy_raises():
+    src = "(strategy)"
+    with pytest.raises(ParseError):
+        parse_strategy(src)